Data Sheet 1_Biochar mitigates dimethylarsenate-stimulated methane emissions mediated by DOM-microbe interactions in paddy soils.docx

Such labile DOM precisely matched substrate requirements of enriched anaerobic fermentative microbes, establishing synergistic metabolic networks to supply methanogenic precursors. DMAs markedly increased mcrA gene abundance by 4.2–7.6 times with negligible change in pmoA, confirming stimulated methanogenesis rather than suppressed oxidation. By contrast, biochar effectively decreased % DMAs in porewater, reducing CH₄ emissions by 54.3% after 2% biochar amendment.

Biochar also decreased DOC concentrations and protein-like DOM (C2, C3), reducing bioavailable substrates for methanogens. Furthermore, biochar suppressed mcrA gene abundances by 12.7–81.3%, while increased that of pmoA gene by 7.1–7.5 times, as well as increased porewater As(V) and enriched ammonia-oxidizing Candidatus_Nitrosopelagicus to potentially or indirectly stimulate anaerobic CH₄ oxidation.</p>Discussion<p>These results establish mechanistic connections between DMAs biotransformation, DOM turnover and CH₄ production in paddy soils, and verify that biochar restructures DOM-microbe interactions to mitigate DMAs-stimulated CH₄ emissions.

This study deepens insights into As-C biogeochemical coupling and offers practical support for simultaneous As remediation and greenhouse gas control in paddy ecosystems.</p>